Interference between Apennines and Hellenides foreland basins around the Apulian swell (Italy and Greece)

The analysis of a set of public seismic reflection profiles allows to unravel the evolution of a segment of the Adria Plate in the Salento offshore, i.e., the Apulian swell (southeastern Italy). The study area was and still is shrinking in the foreland of two orogens and related opposed subduction zones, i.e., the southern Apennines and the Hellenides. The two thrust belt fronts of the opposite and converging orogens become very close (up to 150 km) giving rise, in the Salento offshore, to one of the largest lithospheric anticlines in the world. In this area, the deposits of the Hellenides foreland basin migrated towards W-SW at least from the Oligocene due to the E-NEward flexure of the Adria Plate in the northeastern part of the Ionian sea (i.e., on the area of the future Apulian swell). The same area, arching, was involved in the eastward roll-back of Adria Plate at least from the early Pleistocene, and the sedimentary wedge of the south Apennines foreland basin migrated towards E-NE beginning to occupy the outermost part of the Hellenides foreland basin. Therefore, the two related foredeeps overlapped in time, interfering during Quaternary. From late Early and Middle Pleistocene the area coinciding with the culmination of the arc began to uplift, forming the Apulian swell. While uplifting, the Apulian swell was affected by regularly-spaced normal faults, and became a threshold for sediments coming from the two opposite orogens. Two different narrow depocenters, well separated from each other, represent today the Apennines and Hellenides foredeeps, respectively.